Fibrous web manufacture



p 1961 R. D. HEFFELFINGER ,001,242

FIBROUS WEB MANUFACTURE Filed May 5, 1956 United States P atent U.FIBROUS WEB 'MANUFACI'URE Robert ,D. Heflfelfinger, Lansdowne, Pa.,assignor to American Viscose Corporation, Philadelphia, Pa., a'corporatiou of Delaware Filed May 3, 1956, Ser. No. 582,557

The invention relates to the production of fibrous webs, andparticularlyto a methodfor manufacturing webs having intermingled preformed fibersand fibers formed in situ of flow-able organic plastic compositions.

In a pending application, Method for Producing Filters, of Derek ,E.Till andWorth' Wade, Serial No. 501,933, [filed April 18, 1955, there isdescribed a methodof forming' filters by combining preformed fibers,such as tegrtlle fibers, with other fibers formed in situ. The textileor preformed'fibers are introduced as a loose mass by a blower, or arecut from a continuous tow or strand and dispersed into an air streamwhich separates and delivers the same into the desired area. The fibersformed in situ ar Obta n d bv' e d hs a P c fi -f m m r through aspraying unit which is positioned within a high veldeity air stream. Asmore fully described in said above mentioned application, the fibersfrom both sources are deposited in a random arrangement and in anintermingled relationship to provide a fibrous filter, the filtrationproperties may be varied by controlling the degree fiber interminglingor over-lapping.

In the above mentioned procedure, advantages result by exercisinggreater control over the preformed materials was to deliver the same asa uniform dispersion or airborne cloud of individual fibers which couldbe uniformly mixed with the fibers formed in situ. Accordingly, it'is anobject of this invention to provide a generally new or improved and moresatisfactory fiber delivery method.

Another object is the provision of a method for producing' fibrous websfrom fibers formedin situ, and preformed fibers which are plucked orpulled out from a continuous strand and delivered into a desired area asa cloud or uniformly dispersed mass by a gas stream.

Still another object is the provision of a method for continuouslydelivering and vibrating a textile strand to loosen and pluck theindividual fibers from the strand and disperse the same as a uniformcloud. i These and other objects and advantages of the invention "willbe apparent from the following description and accompanying drawing inwhich:

FIGURE 1 is a diagrammatic elevation, partly in seo tion, illustratingone form of apparatus utilizing the teachings "of the present inventionfor producing continuous fibrous webs; and i FIGURE 2 is a verticalsection, on an enlarged scale, of the aspira'tor device shown inFIGURE 1. r

In generahthe invention relates to the production of fibrous webs bycombining in random and intermingled relationship fibers formed in situand preformed fibers pulled or pluckedfi-om a continuous bundle orstrand and delivered uniformly as a cloud. The in situ fibers are formedby any suitable method and apparatus and preferably in accordance withthe teachings set forth in the above noted pending application, whilethe preformed fibers are loosened and separated from the continuousstrand and uniformly dispersed by an aspirator which subjects the strandto a turbulent and vibrating high velocity gas stream.

With reference to the drawing, the apparatus employed in the practice ofthe method of the present invention includes a chamber or tower 5 havinga fiber forming means 7 and a plurality of aspirator units 9 at one endand, at its opposite end, an endless screen 11 upon which the dispersedfibers are collected in random and inter- Patented Sept. 26, 1961 amingled relationship as hereinafter explained. A suction chest or bol13, connected through a duct 14 to a suitable exhaust source (notshown), facilitates the removal of the gas or air from the chamber 5 andassists in depositingthe fibers upon the screen 11 in their randomandintermingled arrangement.

The fiber forming means 7 includes a circular disc -15 having anupwardly-extending, integral rim or flange 17. A cover plate 19 issecured tothe flange 17 to provide a closed chamber 21 into which aflow-able organic plastic composition is fed. A plurality of spaced,radially extending spray nozzles 23 are mounted on the periphery of therim 17 and communicate with the chamber 21. An impeller comprising 'aplurality of gas-moving vanes 25 is secured to the lower side of thedisc 15. A tubular shaft 27 is connected to the disc 15 and is supportedby bearing 29 for rotary movement applied thereto ,by any suitablesource, such as by a belt and pulley shown at 31 and 33, respectively.In'addition to rotating the disc 15 within the chamber 5, the shaft 27communicates with the chamber 21 and provides a passage through whichthe fiber-forming liquid is delivered from a suitable source (notshown), as indicated by an arrow 35 in FIGURE 1.

The means for delivering the preformed fibers into the chamber 5comprises a plurality of aspirator units 9, preferably located to therear or below and slightly outwardly of the periphery of the impeller25, as shown in FIGURE 1. While two aspirator units 9 have beenillusbra-ted, itis of course obvious that the number can be varied asdesired. Each of the aspirator units, as best seen in FiGURE 2,,includes an angulated suction tube B7which releasably connected, at oneend, to a strand or bundle delivery or feed duct 39 having an enlargedor bell-shaped entrance 41. The opposite end of the suction tube 37 isinclined or tapered at 43 and cooperates with an inclined or taperedsurface 45 of the housing 47 to form an' annular convergent orrestricted orifice or nozzle 49.' The housing 47 is secured ,to thesuction tube 37, preferably by means of cooperating threads, shown at51, which permit relative movement between these partsfand thus enablethe size of the nozzle 49 to be varied; A central annular opening 53passes through the housing 47 and is in alignment'with a central passage55 of the suction tube 37. This housing opening 53 constitutes adischarge tube within which the strand is subjected to a turbulent highvelocity gas stream to effect fiber loosening and separation as morefully explained hereinafter. If desired, the nozzle 49 and dischargetube 53 may be rifled or baflles may be placed in the nozzle to obtainadded gas turbulence or to cause the gas' to travel a spiral path. Theannular area between the suction tube 37 and 'housing47 serves as an airor gas chamber 57 into whichcompressed gas is delivered from a suitablesource (not shown) by a conduit 59, as shown by arrows 61 I Thecompressed gas, issuing through the nozzle 49,

undergoes a rapid expansion upon entry into the discharge tube .53 andis moving at a high velocity. As a result, a vacuum is induced at thedischarge end of the suction tube 37, which in turn produces aninrushing flow of gas or air through the entrance 41 of the duct 39. Thecombined action of the induced vacuum and the inrushing gas is reliedupon for supporting and conveying the strand within and through the duct39 and suction tube 37, and in effect the aspirator unit is consideredto be self-lacing. In view of the low mechanical strength of the yarnbundle or strand, the force of the inrushing gas and vacuum is notrelied upon for feeding the strand to the duct 39, and instead the yarnis mechanically unrolled firom its supply 63 by surface driving means65, which may be of any suitable and conventional construction.

In addition to effecting strand delivery through the duct 39 and tube37, the expanding high velocity gas in the discharge tube 53 impingesagainst the fibers and creates a turbulent gas flow which tends tovibrate and loosen the fibers in the yarn bundle. ,To enable theseloosened fibers to be removed from the yarn bundle or strand and bedispersed into the chamber 5 as a uniform cloud, the strand is subjectedto a retarding or frictional force within the suction tube 37 so thatthe high velocity expanding gas leaving the discharge tube 53 reactsagainst the individual fibers at the leading end of the strand and pullsor plucks the same therefrom. As shown in FIGURE 2, this frictionalforce is created as the strand moves against the edge 67 when itsdirection of travel is altered as a result of the "relatively sharp bendof the suction tube itself. The bend of the suction tube should be assharp as practical, with a right angle bend, as shown in FIGURE 2, beingsatisfactory to properly regulate the pulling or plucking of the fibersfrom the yarn bundle.

In addition to the above described structural aspects of the suctiontube 37, the central passage 55 is preferably of uniform cross-section,with particular care being exercised to avoid an enlarged orbell-mouthed opening in the area of the bend or edge 67 which wouldpermit an expansion of the inrushing air. Further, the length of suctiontube 37 between its bend and its discharge end should be slightly lessthan the staple length employed in the yarn bundle. With thisconstruction, the high velocity gas stream in the area of the nozzle 49and discharge opening 53 at all times reacts against the ends of thosefibers which have moved beyond the suction tube bend and thus are notsubjected to any retarding or frictional forces and can be more easilypulled or plucked from the yarn bundle. The releasable connections ofthe suction tube 37 and housing 47 enable the suction tube to be easilyreplaced as the yarn bundle staple length is varied.

In preparing for operation, the housing 47 of each aspirator unit isfirst adjusted relative to the end of the suction tube 37 to provide thedesired restricted orifice 49. For ease of adjustment, a spacer 69 ofselected thickness is merely placed between the angulated portion of thesuction tube 37 and the terminal portion of the housing 47 (see FIGURE2) so as to obstruct advancing movement of the housing once the desirednozzle opening 49 has been attained. The apparatus is then assembled asshown in FIGURE 1, with the strand supply packages being located asclose as possible to entrance 41 of the feed ducts 39.

In operation, a rotary movement is imparted to the shaft 27 and theflowable spinning liquid is supplied, under pressure, to the chamber 21,and extruded through the spray nozzles 23 by both the supply pressureand the centrifugal force created by the rotating disc. As thefiber-forming liquid leaves the nozzles, it is subjected to both thestatic extrusion pressure exerted in a radial direction and a tangentialforce. The directions of these forces, which are at right angles to eachother, are continnously changing with the rotation of the disc. Theseforces are believed to effect at least a portion of the attenuation ofthe plastic stream. The outermost end of the plastic or fiber is in theair and the extruded plastic which is just emerging from the extrusionorifice is moving in a circular path with the extrusion orifice. Thefriction between the end of the fiber and the air is believed to cause adrag which may account for a part of the attenuation of the plasticStream. The air flow created by the impeller also subjects the fiber toa force which is at an angle to the plane of the extrusion and thetangential forces. As the free end of the fiber is blown upwardly, afurther drag is probably created with respect to the movement of thenozzle. The combined forces and the frictional drag causethe attenuationand stretching of the fiber and the breaking of the attenuated plasticto form discontinuous fibers. During this period, the major 4 portion ofthe solvent becomes volatilized to establish the size of the fibers.

Concomitantly with the above described spinning of the fibers in situ, ayarn bundle or strand is being delivered into each of the aspiratorunits 9 where they are subjected to the vibratoryforces of the highvelocity gas issuing from the nozzle 49. As heretofore described, thefibers are pulled or plucked from the yarn bundle by the expanding gasand carried upwardly toward t-he endless screen 11 where they arecollected in a random and intermingled relationship with the fibersformed by the spin disc. The collected fibers thus form a continuousfibrous web having a uniform intermixture of preformed fibers and fibersformed in situ, and is collected'in a suitable manner as shown at 71.

To insure that the aspirator units function satisfactorily in providinga uniform dispersion of preformed fibers, proper staple selection andfiber lubricant, and careful processing of the fiber bundle are requiredto avoid crimp in the fibers, surface friction, and tangling of thefibers within'the aspirators. A minimum t-wist, commensurate with goodprocessing, should be imparted to the fiber bundle.

During operation, the aspirator units require little supervision oncethe air pressure has been regulated and the rate of fiber feed has beenadjusted, with some care being exercised in the last noted adjustment toavoid overfilling of the aspirator which results in interruptedoperation. In the event the fiber bundle should break, it is onlynecessary to place its free end adjacent to the entrance 41, with theinrushing gas and suction forcm, heretofore explained, effecting theaspirato-r lacing. Should the aspirator become clogged, blocking the endof the discharge tube 53 causes the high velocity air to blow backthrough the suction and delivery tubes to clear the same.

The preformed fibers forming the yarn bundle or strand are preferablynatural or synthetic textile fibers such as for example cotton, wool,silk, rayon, acetate, nylon, Dacron, acrylic fibers and the like. Whilethe yarn bundle or strand has been described as having a slight twist,it is here emphasized that the bundle or strand is actually a continuousloose and soft assemblage of substantially parallel fibers which havebeen twisted to a minimum degree necessary to maintain bundlecontinuity. In effect, the degree of twist utilized adds little ornegligible strength to the bundle.

It is seen from the above description that the objects of the inventionare well fulfilled by the method described. The description is intendedto be illustrative only and it is to be understood that changes andvariations may be made without departing from the spirit, and scope ofthe invention as defined by the appended claim.

I claim: 1

, A process for providing a uniform dispersion of indidividual fibersfrom a continuous yarn bundle formed of preformed fibers extendinggenerally longitudinally of the bundle including the steps of advancingthe leading end of a yarn bundle into a turbulent fluid stream to loosenthe fibers thereof and passing the yarn bundle through an angular pathto retard its rate of advancement at a location spaced from its leadingend to permit the turbulent stream to pluck the loosened fibers from theyarn bundle and disperse the same as a mass of individual fibers.

References Cited in the file of this patent UNITED STATES PATENTS VChichester Apr. 26,

UNITED STATES PATENTS Chesler Mar. 30, 1943 Drill et a1. Sept. 7, 1943Manning Dec. 14, 1943 5 Francis Sept. 5, 1944 Fletcher Oct. 9, 1951 6Stalego Dec. 11, 1951 Ioa Nov. 25, 1952 Schweizer Dec. 15, 1953 ThompsonSept. 2, 1958 FOREIGN PATENTS Australia July 31, 1947

